A systematic study of laser-induced thermal-grating scattering (LITGS) using nitric oxide as an absorbing species is presented as a means of thermometry in air-fed combustion. The relative contributions to the scattered signal from degenerate four-wave mixing, DFWM, and from laser-induced thermal-grating scattering, LITGS, are studied in the time domain for NO in N2 buffer gas up to 4 bar, using a pulsed laser system to excite the (0,0) γ-bands of NO at 226.21 nm. LITGS signals from combustion-generated NO in a laminar, pre-mixed CH4/O2/N2 flame on an in-house constructed slot burner were used to derive temperature values as a function of O2 concentration and position in the flame at 1 and 2.5 bar total pressure. Temperature values consistent with the calculated adiabatic flame temperature were derived from averaged LITGS signals over 50–100 single shots at 10 Hz repetition rate in the range 1600–2400 K with a pressure-dependent uncertainty of ± 1.8% at 1 bar to ± 1.4% at 2.5 bar. Based on observed signal-to-noise ratios, the minimum detectable concentration of NO in the flame is estimated to be 80 ppm for a 5 s measurement time at 10 Hz repetition rate.

中文翻译：

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使用一氧化氮激光诱导光栅光谱进行火焰测温


使用一氧化氮作为吸收物质的激光诱导热光栅散射（LITGS）的系统研究被提出作为空气供给燃烧中的测温手段。使用脉冲激光系统，在时域中研究了高达 4 bar 的 N2 缓冲气体中的 NO，简并四波混频 (DFWM) 和激光诱导热光栅散射 (LITGS) 对散射信号的相对贡献在 226.21 nm 处激发 NO 的 (0,0) γ 带。在内部构造的槽式燃烧器上，使用层流、预混合 CH4/O2/N2 火焰中燃烧产生的 NO 的 LITGS 信号来导出温度值，作为 1 和 2.5 bar 压力下火焰中 O2 浓度和位置的函数总压力。与计算的绝热火焰温度一致的温度值源自 1600-2400 K 范围内以 10 Hz 重复率进行 50-100 次单次发射的平均 LITGS 信号，压力相关不确定性为 ± 1.8%（在 1 bar 至 ± 1.4% 之间）在 2.5 巴。根据观察到的信噪比，在 10 Hz 重复率下测量 5 秒时，火焰中 NO 的最小可检测浓度估计为 80 ppm。